login
Digital root of A179545.
1

%I #24 Mar 08 2022 08:14:59

%S 3,9,3,9,3,9,3,9,3,3,9,9,3,9,3,3,3,9,9,3,9,9,3,3,9,3,9,3,9,3,9,3,3,9,

%T 3,9,9,9,3,3,3,9,3,9,3,9,9,9,3,9,3,3,9,3,3,3,3,9,9,3,9,3,9,3,9,3,9,9,

%U 3,9,3,3,9,9,9,3,3,9,3,9,3,9,3,9,9,3,3

%N Digital root of A179545.

%C Because every term in A179545 is a multiple of 3, each term of this sequence is 3 or 9. - _Nathaniel Johnston_, May 04 2011

%C a(n) = 3 if and only if prime(n) == 2 (mod 3); otherwise a(n) = 9. - _Charles R Greathouse IV_, May 19 2011

%H Nathaniel Johnston, <a href="/A179802/b179802.txt">Table of n, a(n) for n = 1..10000</a>

%F a(n) = A010888(A179545(n)). - _Michel Marcus_, Mar 08 2022

%p read("transforms") ; A010888 :=proc(n) local a; a := digsum(n) ; if a > 9 then return procname(a) ; else return a; end if; end proc:

%p A179545 := proc(n) local p; p := ithprime(n); 3*p*(p-1)/2 ; end proc:

%p A179802 := proc(n) A010888(A179545(n)) ; end proc:

%p seq(A179802(n),n=1..180) ; # _R. J. Mathar_, Oct 03 2010

%o (PARI) apply(p->if(p%3==2,3,9),primes(10000)) \\ _Charles R Greathouse IV_, May 19 2011

%Y Cf. A000040, A010888, A179545.

%K easy,nonn,base

%O 1,1

%A _Odimar Fabeny_, Jul 27 2010

%E More terms from _R. J. Mathar_, Oct 03 2010